By the standards of infants born full-term, pre-term infants are underdeveloped when they are born and often need specialist care and attention. Moreover, aids sometimes made available to infants born full term or to toddlers, etc. are not necessarily appropriate for pre-term infants which are of course physically smaller and require different kinds of stimulation when compared to older infants.
Research conducted into the sort of stimulation most helpful in the development of newborns, for example, by Steri, Lhote, and Dutilleul in Haptic Perception in Newborns Developmental Sciences (3:3 (200) pp 319-327) has purported that Haptic touch is important to development. Haptic touch relates to the feeling, sensation or perception and exploration or manipulation more than to the grasping of objects.
It has also been found that other infirm people, such as the elderly, can benefit from stimulation of the Haptic touch in order to increase his/her dexterity.